The combustion engines used in the automotive field generally comprise an engine block delimiting cylinders that have one end closed by a cylinder head and have sliding within them pistons which are connected to a crank shaft. In four-stroke engines, the cylinder head is provided with intake and exhaust ducts respectively associated with intake and exhaust valves each of which can move between an open position in which it places the cylinder and the corresponding duct in communication, and a closed position in which it isolates the cylinder from the corresponding duct.
To actuate the valves, particularly the intake valves, it is now planned to make use of control devices comprising an electromagnetic actuator associated with at least one valve and connected to a control unit that has been programmed to control the actuator as a function of predetermined parameters regarding the optimal running of the engine, particularly the charge of air to be introduced into the cylinder.
There are various ways of controlling the valves, notably the EIVC and the LIVO modes. In the EIVC mode (this recognized abbreviation originating from the English “Early Intake Valve Closing”), the valve is opened and then closed as soon as the amount of air introduced is sufficient. This method of control makes it possible to reduce the pumping losses which are incidentally often present in engines in which the valves are actuated in the conventional way by a cam shaft. However, this method of control does not encourage the formation of turbulence in the cylinder during air intake, leading to a relatively poor combustion efficiency. In the LIVO mode (this recognized abbreviation originating from the English “Late Intake Valve Opening”) the intake valve is opened late, when power is being produced in the cylinder because of the downward movement of the piston, and is then closed as soon as the amount of air introduced is sufficient, as in the EIVC mode. The pumping losses are higher than in the EIVC mode alone, but the combustion efficiency is improved.